Epidemiological survey of clinical and bacteriological data related to pneumococcal respiratory tract infections by the 31 hospitals of the National Cooperative Survey of pneumococcal infections shows that antimicrobial resistance of S. pneumoniae strains isolated in France since 1984 reaches high levels for erythromycin, tetracycline, sulfa/trimethoprim. The rate of resistance to chloramphenicol is stable and relatively low. For the beta-lactams, change in the susceptible to penicillin G has occured during the period 1986 to 1990. Moste alarming is the high level of resistance (MIC.mg/l: 2-4) exhibited by stains from pneumonia and otitis media wich are multiply resistant and mainly of the 23F serotype. In view of the potential for pneumococci to be resistant to antibiotics often used in these pathologies, antimicrobial susceptibility of all clinically significant isolates should be determined.